In conventional transfer presses, in which a plurality of processing steps are provided in a press main body, a transfer feeder for conveying a workpiece in sequence to a subsequent step is provided between each processing step. A commonly known transfer feeder is a 3-dimensional transfer feeder in which a workpiece is held by workpiece holding jigs, the workpiece being conveyed in sequence to a subsequent step by 3-dimensional direction movement of the workpiece holding jigs in the feed direction (workpiece conveyance direction), clamp direction (horizontal orthogonal direction to the feed direction), and the lift direction.
FIG. 7 shows the overall configuration of a transfer press in which a conventional 3-dimensional transfer feeder is employed.
A transfer feeder 110 has a left/right pair of transfer bars 113 parallel to the feed direction, a plurality of workpiece holding jigs not shown in the diagram for holding a workpiece being detachably mounted in these transfer bars 113. A workpiece 106 is moved in sequence to a downstream-side mold 130 by the 3-dimensional movement operation for the reciprocating feed/return movement in the feed direction (forward-backward movement), the reciprocating lift/down movement (rise-fall movement) in the lift direction (up-down direction) and the reciprocating clamp/unclamp movement (left-right movement) in the clamp direction (direction orthogonal in the horizontal plane to the feed direction) of these transfer bars 113. The fundamental operating pattern of the transfer bars 113 is as follows: clamp, lift, feed, down, unclamp and return. In addition, as devices for facilitating the operation of the transfer bars 113 as described above, a feed device (not shown in the diagram) that provides for movement in the feed direction and a lift/clamp device 140 that provides for movement in the lift direction and clamp direction are provided in the transfer feeder 110.
A feed box 111 in which the feed device is installed is protrudingly provided in either the upstream or downstream side face of a press main body 101 and, in addition, a lift clamp box in which the lift/clamp device 140 is installed is provided between left and right uprights 103 at both the front and rear on a bed 102.
In addition, the patent literature 1 discloses a technology configured from a feed carrier to which a feed bar is connected to allow free movement in the up-down and left-right directions but restrict movement in the forward-backward direction (feed direction), a feed unit for moving the feed carrier forward and backward, and a linear motor serving as a drive source for the feed unit.
Patent literature 1: Japanese Patent Application Laid-Open No. H10-314871